The present invention concerns a technique for installing various cables and a coil to be used in this erection technique and, more particularly, a cable erection technique and a cable erection coil, simplifying the cable erection work and, at the same time, allowing to hold cables in a stable state during and after the erection work.
In general, when various cables such as communication cable or television cable or the like are to be erected, a messenger wire is put up as tensile line between utility poles, and metal hangers such as cable hangers are attached one by one to this messenger wire with an interval of 50 to 60 cm, for hanging cables in parallel.
However, in the cable erection work mentioned above, the operator carries a number of metal hangers, and attaches these hangers moving with an interval of 50 to 60 cm along the longitudinal direction of the messenger wire, and moreover, this hanger attachment operation is done in a height; therefore, such operation has been requiring tremendous time and labor, and considerably high skill.
Of late years, as a method for simplifying the cable erection work, it has been proposed to use an elastic chain coil formed into a continuous spiral from synthetic resin base material. When a cable is erected by means of chain coil, it is possible to insert the chain coil outside the messenger wire, to elongate this chain coil along the messenger wire and, at the same time, to extend the cable inside the coil and fix as it is. Therefore, the cable erection workability can be improved remarkably.
However, while the elastic chain coil presents an advantage of simple erection as mentioned above, on the contrary, when the fastener to the messenger wire is off, or when a part thereof is cut off by an accident or fire due to the component of synthetic resin, the coil shrinks causing such a problem that the cable droops. Besides, when the cable is erected by elongating the chain coil, if the coil fixed end comes off, or the elongated non fixed end is released accidentally, the chain cable shrinks to its original length by its elastic flexibility, obliging to resume the cable erection from the beginning and thus deteriorating its workability.
It is an object of the present invention to provide a cable erection technique and a cable erection coil, simplifying the cable erection work and, at the same time, allowing to hold cables stable during and after the erection work.
The cable erection technique of the present invention to attain the aforementioned object is a cable erection technique using a plastically deformable coil comprising a metal wire formed in a spiral shape and synthetic resin coated on a surface of the metal wire, wherein said coil is inserted outside around a tensile line drawn between utility poles, the coil is elongated until its plastic deformation for forming a series of cable arrangement spaces inside the spiral, and a cable is extended, added or extracted through the cable arrangement space.
Thus, a cable can be extended, added or extracted easily through the cable arrangement spaces, as the plastically deformable coil is inserted outside around the tensile line such as messenger wire drawn between utility poles, and the coil is elongated until its plastic deformation for forming a series of cable arrangement spaces inside the spiral.
Besides, as the aforementioned coil is provide with a property to deform plastically when it is elongated, it is possible to prevent the cable from drooping based on the resistance of plastically deformed coil, even if a coil fastener to the messenger wire is off, or a part thereof is cut off by accident or the like, and the cable can be kept stable for a long time. Besides, the cable does not shrink to its original length even if the coil fixed end comes off, or the elongated non fixed end is released accidentally during the cable erection work; so the cable erection work can be executed efficiently. Moreover, as the aforementioned is provided with metal wire, it can not be cut off by fire.
In the present invention, it is preferable to attach a coil extension device, having a reducing aperture smaller than the outer diameter of the coil, to the coil after having inserted the coil outside around the tensile line, and to elongate the coil until it deforms plastically all the way discharging the coil from the reducing aperture. The use of a coil extension device provided with such reducing aperture allows to improve the operation efficiency of the aforementioned cable erection technique and, at the same time, to set with good precision the coil size during the elongation.
To be more specific, it is preferable to insert the coil outside around the tensile line, then engage one end side of the coil to the tensile line, dispose a coil extension device having a reducing aperture smaller than the outer diameter of the coil at the one end side of the coil, draw the coil extension device to the other end side of the coil along the tensile line, and elongate the coil until it deforms plastically all the way discharging the coil from the reducing aperture. Otherwise, it is preferable to insert the coil outside around the tensile line, then engage one end side of the coil to the tensile line, dispose a coil extension device having a reducing aperture smaller than the outer diameter of the coil at the other end side of the coil, draw the other end side of the coil along the tensile line while fixing the position of the coil extension device, and elongate the coil until it deforms plastically all the way discharging the coil from the reducing aperture.
As tensile line for guiding the aforementioned coil, messenger wire made of a plurality of twisted steel wires, existing cable, complex cable integrating messenger wire and cable (so-called SS type cable) or others can be selected and, if necessary, it can be a temporary rope, or the like.
However, the cable erection technique of the present invention can also be applied to the case without tensile line installation. In this case, using a plastically deformable coil comprising a metal wire formed in a spiral shape and synthetic resin coated on a surface of the metal wire, the coil is elongated until its plastic deformation for forming a series of cable arrangement spaces inside the spiral, and a cable is extended, added or extracted through the cable arrangement spaces. Such cable erection technique is preferable for receiving the cable in the roof-space or under the floor arranging the cable.
In the present invention, cables to be extended, added or extracted include various cables made of a number of buried electric wires, optical wires or the like, such as communication cable, television cable, power transmission cable, or the like and, additionally, service wire and lead-in wire to the office, dwelling or others.
On the other hand, the cable erection coil of the present invention has a structure wherein a resin coated wire comprising a metal wire and synthetic resin coated on a surface of the metal wire is formed in a spiral shape, and is characterized by that said metal wire causes permanent deformation when the coil made of the resin coated wire is elongated.
It is preferable that said metal wire causes permanent deformation when the coil is elongated at least 10 times longer than the non-elongated length thereof. It is preferable the ratio of the cross-section of the metal wire to the cross-section of the resin coated wire is equal or superior to 25%.